1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine and a facsimile machine, and more particularly to a sheet treating apparatus capable of being mounted on an in-body delivery type image forming apparatus delivering a sheet in a space formed between an image-forming portion and an image-reading portion.
2. Description of the Related Art
For example, like a copying machine, a facsimile machine and the like, many image forming apparatus equipped with image-reading portions for reading originals (hereinafter referred to as “scanners”) set the scanners at their upper portions. In particular, almost all of the machines that are used popularly in offices and form images by an electrophotographic process employ the setting.
Moreover, the number of the so-called multiple function processing machines that combine the functions of printers and of copying machines or the functions of printers and of facsimile machines is recently increasing for the purpose of reducing the cost and setting spaces of respective machines.
Moreover, the so-called in-body delivery type image forming apparatus that has decreased installation-space-requirements has been realized. The in-body delivery type image forming apparatus disposes its scanner and its image-forming portion separately to form a space between them, and thereby the apparatus can dispose its delivery tray in a state of not protruding to the outside of the apparatus, which makes the installation space requirements of the apparatus small.
As a concrete example of the in-body delivery type image forming apparatus, a copying machine shown in FIG. 40A was invented. The copying machine includes an image-reading portion 100, an image-forming portion 101 and a delivery space portion 102 for the delivery of sheets. The delivery space portion 102 is disposed between the image-reading portion 100 and the image-forming portion 101. The copying machine disposes its delivery tray or the like, which conventionally protrudes to the outside of the machine, between the image-reading portion 100 and the image-forming portion 101, which makes it possible to decrease the installation space requirements of the copying machine by leaps and bounds.
Even for the space saving image forming apparatus as described above, the following structure is desired. That is, the space saving property thereof is kept by the structure. And, the so-called sheet treating apparatus, which is a sorter performing the sort and alignment of sheets, a finisher performing the processing such as stapling or the like, can be added to the structure as an option. In response to such a demand, an image forming apparatus of a type has already been proposed. The type is one such that a sheet treating apparatus is set in a sheet delivery space in the machine.
However, in the related art, the mounting method of the sheet treating apparatus and the operation efficiency of the mounting are not especially considered. When the sheet treating apparatus is connected with the sheet path (sheet transporting path) of the image forming apparatus, the precision of positioning is needed to be high for the prevention of sheet jamming. However, it was very difficult to perform the operation of the positioning and the like in the narrow sheet delivery space.
Moreover, because the related art structure is structured such that, for example, the sheet treating apparatus is mounted in the delivery space portion of the image forming apparatus and the image forming apparatus forming the space is disposed at an immediately upper part of the sheet treating apparatus, the space for stacking sheets on which images have been formed on a stacking tray of the sheet treating apparatus is narrow. Consequently, the related art structure has a problem. The problem is that the number of stackable sheets is limited.
Moreover, the related art structure makes it possible to reverse the surfaces of sheets by utilizing the delivery space portion in the case where images are formed on both the sides of the sheets. To put it concretely, as shown in FIG. 40B, the related art structure begins to deliver a sheet, on which an image has been formed by image forming means 103, with a delivery roller 104 for the time being. Next, the structure reverses the delivery roller 104 at a predetermined position to draw the sheet into the structure. Then, the structure transports the drawn sheet to the image forming means 103 again through a re-feed path 105 to form an image on the opposite side of the sheet. After that, the structure executes the operation of the delivery of the sheet to be stacked in the delivery space portion 102 with the delivery roller 104 again.
By employing the aforesaid structure, the related art can omit the structure of a surface reversing portion and the like that are needed in conventional structures, and thereby the related art can realize further miniaturization and the reducing of the cost.
However, it has recently been invented to dispose a treating apparatus 106 for executing stapling processing, sorting processing and the like in the delivery space portion 102 as shown in FIG. 41 for the coexistence of the space saving property thereof and the high productivity thereof. In the case where the treating apparatus 106 is set in the delivery space portion 102 in the copying machine that is possible to reverse the surfaces of sheets and was described with respect to the related art, it becomes necessary for the machine to be equipped with transportation rollers 106b, which receive a sheet delivered from the delivery roller 104 on the side of the main body of the machine and transport the received sheet to a treating portion 106a such as a stapler, a guide 106c and so forth.
When it is tried to reverse a sheet by reversing the delivery roller 104 conventionally in a copying machine mounting the treating apparatus 106, as described above, because the related art image forming apparatus operates such that the trailing end of a sheet on one side of which an image is recorded protrudes from a delivery port and is transported into the image forming apparatus at the time of reversing in case of duplex recording, the guaranteed stackable height, or the regulated value of the fully stacked height, of the related art image forming apparatus should be set at a lower value with a margin lest a surface-reversed sheet should push out an already stacked sheet. Moreover, the related art image forming apparatus has inconvenience. The inconvenience is that the apparatus will give a user an uneasy impression at the sight of the manner such that a sheet has once gone out and enters into the main body again.
Moreover, the surface reversing operation of the related art image forming apparatus in the state of setting the treating apparatus 106 is performed as follows. That is, an end portion of a long sheet enters into the reception portion, and then the long sheet passes through a nip by the transportation rollers 106b of the treating apparatus 106. After that, the long sheet is reversed.
When a stepping motor is used for the control of the transportation rollers 106b, the related art image forming apparatus consequently has a possibility of bringing about buckling, step-out and the like because suitable synchronization cannot be realized owing to the fact that different controllers are used for the delivery roller 104 of the main body of the image forming apparatus and the stepping motor. For the prevention of this possibility, it becomes necessary to add a new mechanism for releasing the nip of the transportation rollers 106b of the treating apparatus 106.
For the prevention of these problems, it becomes necessary to take the following measures. That is, the distance between the delivery roller 104 on the main body and the transportation rollers 106b is set to be large. In other words, the distance between the delivery roller 104 in the delivery space portion 102 and the treating apparatus 106. However, when the treating apparatus 106 is kept at a distance from the delivery roller 104, the treating apparatus 106 protrude from the main body of the copying machine, which impedes the achievement of the object of space saving.
Also the problems of increase in size and cost are produced because the mechanism for releasing the nip of the transportation roller 106b and other mechanisms are added.
Next, there is an image forming apparatus in a structure with a stack tray that can lift/lower and is disposed on the side of the image forming apparatus as an image forming apparatus capable of stacking a great many sheets on which images have been formed and stacks of sheets that have been subjected to an aftertreatment such as stitching after the formation of images. The height position of the uppermost sheet stacked on the stack tray is detected and adjusted by, for example, a sheet surface detection lever and a sheet surface detection sensor.
However, the related art image forming apparatus is worried about the following thing.
Because the stack tray is situated on the outside adjoining the image forming apparatus, then even if a sheet-aftertreatment apparatus is disposed between an image-reading portion and an image-forming portion, it is difficult to form the image forming apparatus in a small size. Accordingly, it is considerable to dispose the stack tray, too, between the image-reading portion and the operation portion of the main body of the image forming apparatus, and the image-forming portion. However, only by the employment of such a disposition, the stack tray is disposed immediately under the image-reading portion and the operation portion. Consequently, when a user looks the image-reading portion and the operation portion down from an upper position for taking out sheets or stacks of sheets that have been delivered on the stack tray, the stack tray is overlapped with the image-reading portion and the operation portion at a position immediately under them and the user cannot look at the sheets or the stacks of sheets that are stacked on the stack tray. Accordingly, the user is obliged to take out the sheets or the stacks of sheets by groping for them to grasp them. Consequently, the image forming apparatus is inferior in visibility and taking out property.
It is considerable that the space between the image-reading portion and the operation portion, and the tray portion is widened as a structure for resolving the problem. Such a structure improves the visibility and the taking out property. However, the structure brings about the increase of the heights of the image-reading portion and the operation portion, and the whole height of the image forming apparatus is consequently heightened by the degrees. Consequently, it is considerable that the increase of the heights brings about the difficulty of the user s setting of originals on the image-reading portion, and that the increase of the heights brings about the increase in size of the image forming apparatus.
Moreover, because the stack tray rises and falls, the stack tray sometimes vibrate when it begins to rise or to fall, or during it is lifting or lowering, or when it is stopping. It is the possibility that the vibrations cause the following problems.
At first, there is a case where the stackability is impaired because the positions of the sheets, which have already been stacked on the tray, are shifted owing to the vibrations. Or, when the sheet surface detection lever receives the vibrations and vibrates synchronously with the vibrations, the vibrations of the sheet surface detection lever causes the chattering of a sensor for detecting the operation of the sheet surface detection lever to make it impossible to detect the position of the stack tray. Consequently, there sometimes happen the following cases. That is, the sheets and the stacks of sheets are not stacked at a predetermined position on the stack tray, or even if they are stacked at the predetermined position, they are not stacked in good order. This state makes it difficult for a user to grasp them.
For a method for preventing the chattering of the sensor, it can be considered not to make the sheet surface detection lever vibrate even if the stack tray vibrates by increasing the lowering amount of the stack tray and by making the stack tray descend up to a position where the upper most sheet of the sheets or the stacks of sheet that are stacked on the stack tray is not contact with the sheet surface detection lever. However, the method enlarges the space in the vertical direction of the apparatus by the lowering amount of the stack tray. Consequently, the method causes a problem that the height of the image forming apparatus becomes high.